1. Field of the Invention
The present invention relates to failure diagnosis of a brake switch for detecting an operation condition of a brake pedal of a vehicle such as motor vehicle, and particularly relates to a method and a system for achieving failure diagnosis with a simple configuration, improved reliability and the like.
2. Description of the Related Art
As this type of system, various systems have been proposed in the past, including a system as shown in Japanese Patent Publication No. 2,772,737, which is configured to synthetically determine the presence of failure of a brake switch from internal pressure of a booster for boosting braking liquid pressure and variation of the internal pressure, brake pedal force applied to a brake pedal, and braking pressure.
However, in the system disclosed in the patent publication, while many determination elements are used and therefore highly reliable diagnosis may be expected, since the system requires a signal depending on booster pressure, and a signal depending on brake pedal force, and furthermore a signal depending on braking pressure, increased number of sensors are required for a vehicle as a whole, in addition, number of wirings is increased, the wirings connecting between the sensors and an electronic control unit performing electronic control of the vehicle. Consequently, the system has not always been acceptable for a vehicle being limited in space for setting components, and desired to have a simple configuration and reduced number of the components to the utmost.